Active wheel speed sensors can be used to determine the speed of vehicle wheels and to provide that information to vehicle control modules, such as, for example, an anti-lock brake system (ABS). At times it may be desirable to test a wheel speed sensor to determine whether it is properly functioning. Many types of active wheel sensors have previously been tested while connected to the vehicle wiring harness through a breakout box. This process can be cumbersome and time consuming.
One type of sensor testing approach is described in U.S. Patent Application 2005/0262921. The disclosed tester is for in situ testing of an active wheel speed sensor, and includes a window comparator block that creates voltage outputs representing pass-fail criteria for the active sensor. The output of the comparator is connected to a plurality of LEDs. Illumination of the LEDs indicates the operating states of the sensor, such as valid high state, valid low state, open circuit, short circuit, etc.
The inventor herein has recognized several disadvantages with the sensor testing solution of U.S. Patent Application 2005/0262921. In particular, the tester may not be used to easily test the sensors in various different vehicles, since different vehicle models may have different wiring harness connectors, and the sensors and/or wiring harnesses may employ different polarities. Furthermore, the above device is not configured to identify problems associated with the ABS circuit or wiring, which may result in erroneous messages that the sensor is malfunctioning.